Biological Control Agent: Brachypterolus pulicarius L.
Type of Agent: Seed feeding beetle
Status
Tertiary
Description and Biology
Adult:
The beetles are shiny black, elongate to oval, 2.4 x 1.0 mm, and sparsely covered with
hairs. Short wing covers expose the last abdominal segments of their bodies. Females
have slightly longer covers than the males. Rear legs are darker than the other legs.
Near equal male/female ratio adults begin to appear in early May, usually when the plants are
15 - 20 cm tall. Adults congregate and feed on pollen, flowers and on young foliage,
sometimes completely consuming terminals. Mating occurs in June when the plants begin
to bud. Heavy feeding can cause significant flower loss, which may delay oviposition
until the second flowering cycle in July. Eggs are laid individually or in small clusters
of up to three into unopened floral buds. Adults live one to three months and populations
begin to subside by August.
Egg:
The eggs are white and measure 0.6 mm long. Just prior to hatching, the eggs turn
yellow.
Larva and pupa:
Pale yellow larvae with brown heads emerge and begin feeding on the reproductive parts
of the flowers and move between flowers and developing buds. Smaller flowers are less
nutritious than larger ones and, therefore, the quantity of floral damage each larva destroys
relates to bloom size. Older larvae will feed on seeds. Mature larvae move into the soil
to pupate. Yellow pupae measure 2. 8 x 2. 0 mm and develop for three weeks.
Overwintering stage:
Most overwinter as pupae, however, adults can overwinter in climates with long growing
seasons.
Location and effectiveness of attack
Adults feed first on early succulent terminal growth, causing extensive damage and later
move onto flowers and floral buds as they become available. Stem and terminal damage
initiates branching. Heavy attack causes delayed bloom until July or August. Larvae feed
on the reproductive parts of the plants and developing seeds.
Brachypterolus pulicarius feeding
reduces the first bloom by 95%; the second by 82%; and, the third by 52%. Overall seed
production is reduced by 74% and each beetle is responsible for destroying 76.5 seeds.
Heavy foliar feeding can help reduce plant vigour.
Predicted and native habitat
The adventive biocontol agent, B. pulicarius is abundant and common in all Canadian
provinces that support yellow and Dalmatian toadflax varieties. It shows a preference
for yellow toadflax but is commonly found on both. It has a broad range of climatic and
habitat preferences, from warm to hot open sites, to warm, slightly moist semi-shaded locations.
Sites with coarse sandy and poor soils are common with the plant and B. pulicarius.
In Europe B. pulicarius is wide spread.
British Columbia Experiences
Origin:
It is unknown where the source of the B. pulicarius populations
found in BC originate from.
History:
B. pulicarius was found in Saskatchewan by 1950. It is believed to have entered
into Canada via the accidental introduction from New York, where it was first noticed in 1919.
The first B. pulicarius release in BC was made near Grand Forks in 1989.
No further assisted redistribution efforts continued because it was found to
already be well established in BC.
Habitat:
B. pulicarius is found in the Bunchgrass, Coastal western hemlock, Interior cedar
hemlock, Interior Douglas-fir, Ponderosa pine and Sub-boreal spruce biogeoclimatic zones.
Field results:
B. pulicarius
has self dispersed and is commonly found throughout the toadflax infestations and appears to
have no preference for one variety over the other. Early reports show
that toadflax inventory and B. pulicarius dispersal occurred in many
areas of BC. Although it may not be present in
its adult form at the same time as other biocontrol agents, it is often found sharing sites
with Rhinusa spp., Calophasia lunula, and Mecinus janthinus.
Wide dispersal of this agent eliminates the need to collect and release B. pulicarius in
most circumstances. Adults can be swept from plants in early summer. Aspirating
adults is efficient and less destructive to plants.
Notes
B. pulicarius directly competes with Rhinusa antirrhini and R. neta.
References
Harris, P. 1961. Control of toadflax by Brachypterolus pulicarius (L.)
(Coleoptera: Nitidulidae) and Gymnaetron antirrhini (Payyk.) (Coleoptera: Curculionidae)
in Canada.
Harris, P. 2005. Classical biological control of weeds established biocontrol
agent Brachypterolus pulicarius L. flower-feeding beetle. Gov. of Can., Agriculture
and Agri-Food Canada. February 1, 2007. http://res2.agr.ca/lethbridge/weedbio/agents/abracpul_e.htm
Hervey, G. E. R. No date. A European Nitidulid, Brachypterolus pulicarius L.
(Coleoptera, Family, Nitidulidae). Journal of Economic Entomol., Vol. 20: 809-814.
MFR staff comments and observations
Powell, G. W., A. Sturko, B. Wikeem and P. Harris. 1994. Field guide to the
biological control of weeds in British Columbia. B.C. Min. For. Res. Prog.
Rees, N. E., Quimbly, Jr., P. C., G. L. Piper, E. M. Coombs, C. E. Turner, N. R. Spencer,
L. V. Knutson (editors). 1996. Biological control of weeds in the west.
Smith, J. M. 1959. Notes on insects, especially Gymnaetron spp. (Coleoptera:
Curculionidae), associated with toadflax, Linaria vulgaris Mill. (Scrophulariaceae), in
North America. The Can. Entomol., Vol. XCI, No. 2. Pp. 118-119.
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